Alan Greenspan

"Before I met Ayn Rand, I was a logical positivist, and accordingly, I didn’t believe in absolutes, moral or otherwise. If I couldn’t prove a proposition with facts and figures, it was without merit. In the midst of a conversation, she said to me, “Do I understand the thrust of your position? You are not certain you exist?” I hesitated a moment, and I said, “I can’t be sure.” And she then said to me, “And who, by chance, is answering that question?” With that little exchange, she undermined the philosophical structure I had built for myself. "